Given two sorted integer arrays arr_a and arr_b, and two integers len_a and len_b representing the number of valid elements in arr_a and arr_b respectively, merge arr_b into arr_a so that arr_a contains all elements from both arrays in non-decreasing order. arr_a has a length of len_a + len_b, with the first len_a elements valid and the rest reserved for merging. The merged result must be stored in arr_a in-place.
Example 1
Input: arr_a = [3, 4, 7, 0, 0, 0], len_a = 3, arr_b = [1, 5, 8], len_b = 3
Output: [1, 3, 4, 5, 7, 8]
Explanation: Merge [3,4,7] and [1,5,8] into arr_a.
Example 2
Input: arr_a = [2, 0], len_a = 1, arr_b = [1], len_b = 1
Output: [1, 2]
Explanation: Merge [2] and [1] into arr_a.
Example 3
Input: arr_a = [0], len_a = 0, arr_b = [4], len_b = 1
Output: [4]
Explanation: Merge [] and [4] into arr_a.
Constraints
Case 1
Input: arr_a = [6, 9, 10, 0, 0, 0], len_a = 3, arr_b = [2, 7, 11], len_b = 3
Expected: [2, 6, 7, 9, 10, 11]
Case 2
Input: arr_a = [5, 0, 0], len_a = 1, arr_b = [1, 3], len_b = 2
Expected: [1, 3, 5]
Case 3
Input: arr_a = [0, 0, 0], len_a = 0, arr_b = [-1, 0, 2], len_b = 3
Expected: [-1, 0, 2]
Case 4
Input: arr_a = [7, 8, 9, 0, 0], len_a = 3, arr_b = [1, 2], len_b = 2
Expected: [1, 2, 7, 8, 9]
Case 5
Input: arr_a = [1, 2, 3, 0], len_a = 3, arr_b = [4], len_b = 1
Expected: [1, 2, 3, 4]